/* Copyright (C) 2004 - 2006  db4objects Inc.  http://www.db4o.com

This file is part of the db4o open source object database.

db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL 
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.

db4o is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
namespace Db4objects.Db4o.Internal
{
	internal class WeakReferenceCollector : Sharpen.Lang.IRunnable
	{
		internal readonly object _queue;

		private readonly Db4objects.Db4o.Internal.ObjectContainerBase _stream;

		private Db4objects.Db4o.Foundation.SimpleTimer _timer;

		public readonly bool _weak;

		internal WeakReferenceCollector(Db4objects.Db4o.Internal.ObjectContainerBase a_stream
			)
		{
			_stream = a_stream;
			_weak = (!(a_stream is Db4objects.Db4o.Internal.TransportObjectContainer) && Db4objects.Db4o.Internal.Platform4
				.HasWeakReferences() && a_stream.ConfigImpl().WeakReferences());
			_queue = _weak ? Db4objects.Db4o.Internal.Platform4.CreateReferenceQueue() : null;
		}

		internal virtual object CreateYapRef(Db4objects.Db4o.Internal.ObjectReference a_yo
			, object obj)
		{
			if (!_weak)
			{
				return obj;
			}
			return Db4objects.Db4o.Internal.Platform4.CreateYapRef(_queue, a_yo, obj);
		}

		internal virtual void PollReferenceQueue()
		{
			if (_weak)
			{
				Db4objects.Db4o.Internal.Platform4.PollReferenceQueue(_stream, _queue);
			}
		}

		public virtual void Run()
		{
			PollReferenceQueue();
		}

		internal virtual void StartTimer()
		{
			if (!_weak)
			{
				return;
			}
			if (!_stream.ConfigImpl().WeakReferences())
			{
				return;
			}
			if (_stream.ConfigImpl().WeakReferenceCollectionInterval() <= 0)
			{
				return;
			}
			if (_timer != null)
			{
				return;
			}
			_timer = new Db4objects.Db4o.Foundation.SimpleTimer(this, _stream.ConfigImpl().WeakReferenceCollectionInterval
				(), "db4o WeakReference collector");
		}

		internal virtual void StopTimer()
		{
			if (_timer == null)
			{
				return;
			}
			_timer.Stop();
			_timer = null;
		}
	}
}
